Cloning the sample app

The sample app is available on GitHub atGoogleCloudPlatform/getting-started-python.

1. Clone the repository.

   gitclonehttps://github.com/GoogleCloudPlatform/getting-started-python.git

2. Go to the sample directory.

   cdgetting-started-python/gce

3. Because the app only returns "Hello World!", it requires no configuration, andyou can run it right away.

   gcloudappdeploy

4. To see the returned message, enter the following URL in your browser:

   https://PROJECT_ID.REGION_ID.r.appspot.com

   Replace the following:

   • PROJECT_ID: Your Google Cloud project ID
   • REGION_ID: Acode that App Engine assignsto your app

Creating an uptime check

After you deploy your app,you can use Monitoring to create an uptime check. The checkcontinually pings your deployed app to ensure that it's returning a healthyresponse.

1. In the Google Cloud console, go to the Uptime checks page:

   Go toUptime checks

   If you use the search bar to find this page, then select the result whose subheading isMonitoring.

2. ClickCreate Uptime Check.

3. Give your check a title, such asCheck Hello World,and then clickNext.

4. In theTarget section, you specify what the uptime check is to monitor:

   1. Because you deployed to App Engine, changeResource Type toApp Engine instead ofURL. (URL is for generating a customURL on a Compute Engine instance.)
   2. Select theService to be monitored by the uptime check.
   3. LeavePath blank to default to the main index page.
   4. LeaveCheck frequency at the default of1 minute.
   5. ClickNext.

5. Leave theResponse Validation fields at their default values andclickNext.

6. In theAlert & Notification section, you specify how you are notifiedif an alert occurs:

   • Ensure that the toggle's label isAlerting is enabled.
   • Leave the name and duration fields at their default values.

   • To add a notification channel to the alerting policy, in thetext box labeledNotification channels, clickMenu.Select the channels to add and clickOK.The notifications are grouped alphabetically for each channel type.

     To add an entry to the checkbox list, clickManage notification channels and follow the instructions. When youreturn to this dialog, clickRefreshrefresh.

7. ClickCreate. When the create action is successful, the messageCheck and alert created is displayed and then theUptime checksdashboard page is displayed.

   In the uptime checks dashboard, your new uptime check is listed. If youclick the check name, then you open the detail view for that uptime check.This view displays several charts, shows the uptime percentage and theconfiguration information, and lists the configured alert policies.To view a policy, click its name.

   You can also view the alert policy by starting at theAlerting page.From the alerting page, thePolicies pane lists a subset of policies.To view a list of all policies, clickSee all policies.

Simulating an outage

Now that the uptime check is created, you can simulate an outage by changingyour app to respond with an HTTP404 Sorry, we can't find that page errorrather than an HTTP200 OK response.

1. The following code shows where the Hello World app returns only a 'HelloWorld!' message, and that the status code of the response defaults to200 OK.To view this code in the Hello World app, use the view function.

   # Copyright 2019 Google LLC All Rights Reserved.## Licensed under the Apache License, Version 2.0 (the "License");# you may not use this file except in compliance with the License.# You may obtain a copy of the License at##     http://www.apache.org/licenses/LICENSE-2.0## Unless required by applicable law or agreed to in writing, software# distributed under the License is distributed on an "AS IS" BASIS,# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.# See the License for the specific language governing permissions and# limitations under the License.fromflaskimportFlaskapp=Flask(__name__)@app.route('/',methods=['GET'])defsay_hello():return"Hello, world!"if__name__=='__main__':app.run(host='127.0.0.1',port=8080,debug=True)

2. To cause the Hello World app to return an HTTP404 error code, change thereturn line by adding a404 value to the second part of the return value.

   return'Hello World',404

3. Deploy the new, intentionally broken app.

   gcloudappdeploy

   Within half an hour, you'll receive an email message that states that youruptime check is failing.